I've got a fridge with 4 faucets. I've been using it for about a year now with no problems. I purchased another used keg and rebuilt it. I've used this keg twice now. The first time an ESB was pouring all foam. I transferred to another keg and now it's fine. Just kegged and carbed an IPA in that same keg (after rebuilding it) and now it's pouring the IPA all foam. I can see foam in the beer line from the keg to the faucet. There are no CO2 leaks. All 3 kegs are at the same temp (38) in the fridge. All lines are the same length. I've had other kegs hooked to this faucet with no issues. Keg and all lines were cleaned with PBW, rinsed and sanitized with StarSan. CO2 is at 10 lbs as all are pale ales. The other two kegs are pouring perfectly.

What could possibly be wrong with this keg that caused it to be pouring foam? I changed all 5 seals and there are no leaks. Weird...

Changed out the poppet. Seems to have improved a bit but still have some foam in the line. Keg is a bit warm after the work so I'll let it cool back down and check again. If that doesn't work I'll change to a different line in case the QD isn't working correctly. Glad the other kegs are working so I'll have something to do while I wait.

I have a similar condition and I believe (but am not certain yet) that it may be due to different faucet styles. Two of my faucets are perlick and one is a standard cheapo model. The cheapo pours considerably more foam than the perlick model faucets. Same line length, diameter and it matters not which keg I use, so I am leaning to the faucet itself.

I could see that. Turns out it was my poppet so thanks to Brewfat. I disassemble and clean my faucets every Sunday. I went a month once and it was nasty. Could be because my fridge is outside in South Florida, but I didn't realize it was so important until I saw the mold on the piston. Thank goodness I wasn't using that faucet at the time. Takes me 10 minutes to clean 4 faucets and damn well worth it.